It is known in the art relating to flexible assembly systems to use a batch build method or a synchronous method. In a synchronous method, the batch size is one. Synchronous production methods typically use multiple presses without changing the die in any of the presses. Use of multiple presses requires a large amount of space and is associated with high machinery costs. On the other hand, batch production methods, such as in the production of vehicle closure panels, often use press and die hemming apparatuses with die changers. Conventional die change methods, however, are time-consuming and decrease production speed. For example, for automotive closure panel assembly lines, production speeds are typically in the range of 50 to 120 jobs per hour.
In conventional press applications, the home position of the press is an open position. The first step in the operational sequence is the part is loaded onto the lower die, and the press cycles to a closed position and returns to the open position to complete a work stroke. During the work stroke, the press performs work on a workpiece via a die held by the press. To change the die, a workpiece or part inside the die is first removed from the die and/or transferred to another station. Then the die is moved from the open home position to the closed position. The upper die is released and the press raises to the home position, leaving the upper die on the lower die. The die is then shuttled out of the press and a new die is shuttled into the press. The press then lowers to the closed position, and the upper die is clamped to the press. The press then raises back to the home position and is ready to perform work on a new workpiece.